Consumer are demanding smaller bulk packages that incorporate greater functionality (i.e., one-by-one product presentation and resealability). These bulk packages, especially bulk packages that must also have other functional requirements, such as moisture-resistance and resealability, is particularly challenging to produce because the functional requirements often necessitate the use of multiple parts and materials. However, the use of fasteners to join components together adds to the component count and, most importantly, takes up valuable space.
Two-shot or multi-shot injection molding allows different materials having different functional properties to be molded into a single part without the need to use fasteners to join the materials together. The two materials are typically joined to each other by means of a weld defined by the interface solidification of melted portions of the two materials. In order to form such a weld, however, the different materials must be chemically similar or compatible. This limits the selection of materials that can be used to fabricate the molded part.
There is still a need for an injection molding method that enables mechanical interlocking to occur between dissimilar materials, thereby maximizing the functionality of the component part without regard to chemical similarity or compatibility of the materials, and without the need to employ separate fasteners or utilize adhesives.